Electrostatic recorder with plural electrodes and biased mask



March 5, 1968 H. EPSTEIN ET L 3,372,400

ELECTROSTATIC RECORDER WITH PLURAL ELECTRODES AND BIASED MASK Filed Dec. 5, 1962 4 Sheets-Sheet 1 PUT/41?) SOLE/VOID PULSE (ONT/70L CAPJTA V TAKE-UP REELZ;

H. EPSTEIN ET AL 3,372,400

4 Sheets-Sheet 2 is 0&715072 Tfwzazson 7 March 5, 1968 ELECTROSTATIC RECORDER WITH PLURAL ELECTRODES AND BIASED MASK Filed Dec. 3, 1962 6% NW ww W;

March 5, 1968 ELECTROS EPSTE|N ET AL 3,372,400

TATIC RECORDER WITH PLURAL ELECTRODES AND BIASED MASK Filed D80. 5, 1962 4 Sheets-Sheet 5 ZZ/671507151 Herman, .ZZvafez'n George CZ H42 7*72'5 fdwardffk anson United States Patent Ufiice 3,372,400 ELECTROSTATIC RECORDER WITH PLURAL ELECTRODES AND BIASED MASK Herman Epstein, Philadelphia, and George A. Harris,

Malvern, Pa Edward M. Johnson, Detroit, Mich, and

Thomas L. Thourson, Arlington Heights, Ill., assignors,

by mesne assignments, to Borg-Warner Corporation,

Chicago, 13]., a corporation of Iliinois Filed Dec. 3, 1962, Ser. No. 241,839 9 Claims. (Cl. 34674) This invention relates in general to an electrostatic recording system for (l) printing or imposing electrostatic charges on selected areas of a flexible dielectric medium to define a latent image, (2) inking or rendering the latent image visible by applying opaque particles which adhere to the charged areas of the medium, and (3) fixing the particles in place to provide a permanent record. More specifically, the present invention is directed towards an improved printing head or charging station.

With the advent of high-speed data-processing systems such as those including digital computers, the speed at which information can be processed has been substantially increased. Accordingly, a definite time lag has developed between the rate at which information can be handled within the computer itself and the rate at which the information can be supplied to, and/or read out from, the computer. To bridge this gap in the over-all data handling picture, various high-speed equipments have been developed. By way of example, one such equipment is an electrostatic recorder which forms visible, information-representing marks and/or characters on a moving tape from information supplied by a computer during readout, or compiled from other sources and inserted on the tape to provide a suitable source for feeding information into the computer at a high speed.

In certain electrostatic recorders a dielectric medium such as a tape comprised of polyethylene or vinyl plastic with a conductive backing surface is fed through a charging station, at which station a recording head issues electrical discharges which are directed onto the moving tape in certain areas to define a latent image. One such recording head is disclosed and claimed in Patent No. 3,124,804, which was issued on Mar. 10, 1964, to Herman Epstein and Edward M. Johnson, and is assigned to the assignee of this invention. Thereafter the tape carrying the charged areas is passed through an inking station which contains a supply of conductive powder, such as a mixture of resins and carbon. The particles are attracted to the charged surface areas and adhere thereto, rendering the latent image visible. Some means may be provided for removing excess powder from the background or uncharged portions of the tape, thus sharply defining the image. The inked (or, more precisely, powdered) areas on the tape are then permanently fixed by various means such as the application of heat, pressure, coating with lacquer, or other known means.

Such electrostatic recording systems are capable of very high speed operation, especially as contrasted to older systems which utilize mechanical means for punching holes or slots in a tape or a card. In such punching arrangements, the tape is stepped or displaced in increments, being halted as the punch means is operated to produce apertures at the desired locations. In contradistinction to such step-by-step displacement, an electrostatic recorder can effect the charging and printing operations on the fly, with the tape continuously moving, to minimize wear on the mechanical portions of the system. If desired, step-by-step operation can also be provided with an electrostatic system. Having thus reduced system wear while at the same time substantially increasing the operating speed of the system, there still remain areas in which 3,372,400 Patented Mar. 5, 1968 the efiiciency of the electrostatic improved.

For example, the efiicient electrostatic recording head disclosed and claimed in the patent identified above utilizes a single input electrode and a single output electrode for depositing the charge on a given surface area of the tape. It is an important object of this invention to provide an improved recording head, one in which the definition, density and shape of the charge deposited on a given surface area are significantly improved over the results obtained with only a single input and a single output electrode in each channel.

A related object of the invention is the provision of means for regulating the charge distribution characteristics.

Another important object of the invention is the provision of means for guiding the electrical discharges into the desired tape areas.

The foregoing and other objects are realized, in one embodiment of the invention, by providing a printer head and associated components including a tape guide which is readily displaceable to permit the insertion of the flexible tape laterally and is then returned to its working position to maintain the tape in its desired position. The head includes a plurality of electrode arrays, each array comprising more than two electrodes and being positioned so that one charge area is deposited by a single array of electrodes. In certain embodiments it has been found desirable to enhance the charge area definition by interposing a non-conductive mask between the electrode arrays and the flexible tape, the mask defining a plurality of apertures with each aperture aligned beneath an individual array of electrodes.

In other embodiments the mask is formed at least partially of conductive material, and can be left floating, in an electrical sense, or can be coupled to a plane of reference potential, such as ground. In the alternative, a direct-current (D-C) voltage can be applied to the mask in time coincidence with the passage of the charged particles from the electrodes to the tape. Another embodiment of the invention includes the concomitant application of more than one form of bias, such as the superposition of a pulsating or alternating bias upon a D-C bias potential of reference level.

In order to acquaint those skilled in the art with the best mode contemplated for carrying out the invention, a description thereof is set forth in connection with the accompanying drawings, in the several figures of which like reference numerals denote like elements, and in which:

FIGURE 1 is a perspective illustration of the inventive system;

FIGURE 2 is a schematic diagram, partly in block form, depicting the intercoupling of various control and operating components of the system shown in FIGURE 1;

FIGURE 3 is an illustrative drawing representing the operation of certain components shown in FIGURE 2 as a function of the movement of another component depicted in FIGURE 1;

FIGURE 4 is a front view of one component of the system set forth in FIGURE 1, taken on an enlarged scale;

FIGURE 5 is a side view, partly broken away, of the component shown in FIGURE 4;

FIGURE 6 is a partial sectional view, taken on the line 6-6 of FIGURE 5 and on a scale enlarged with respect thereto, illustrating a portion of this component;

FIGURE 7 is a partial sectional view, taken along the line 7-7 in FIGURE 4 and on a scale enlarged relative thereto, illustrating this component of the invention including the manner in which the tape is readily inserted laterally;

printing system can be FIGURE 8 is a partial illustrative showing, taken where indicated by line 8--8 in FIGURE 7, illustrating the relation of the mask to the electrode arrays in this embodiment;

FIGURE 9 is a perspective view of a mask together with a mounting member affixed to the mask to facilitate insertion and removal of the mask beneath the printing head; and

FIGURES 1013 are schematic diagrams, partly in block and symbolic form, illustrating various embodiments of the invention.

General system description In FIGURE 1 various componentsof the invention are depicted, and the direction of tape movement through the system is shown. In general, the flexible tape is provided upon a supply reel 21, and moves from this reel past a printing station 22, an inking station 23, and a pressure fixing station 24 to a take-up reel 25. In addition to these major components or units, other cooperative elements of the system are also shown.

More specifically, tape 29 travels from supply reel 21 over an arbor or roller 26, where its direction is changed, and approaches brake unit 27. The brake assembly comprises a fixed lower unit 28, and a movable upper unit 29 supported over a spring unit 19 affixed to mounting block 18. Although the brake unit, as well as the drive capstan unit 39 which comprises upper and lower rollers 31 and 32, respectively, is positioned adjacent the printing station, these assemblies have nothing to do with the imprinting or positioning of the charged areas on the tape but affect only movement of the tape through the system.

Printing station 22 includes a head 33 positioned over the tape and a common electrode or anvil unit 34 disposed thereunder. A pulse control unit 35 is depicted in block form, and it is this unit which supplies high voltage pulses to the printing head 33 to establish a mass of charged particles for displacement onto the tape. Because the construction and operation of assemblies for producing and applying voltage pulses of practically any desired amplitude and waveform are well known and understood in the art, no further reference will be made to the pulse control unit 35.

As the tape passes the printing station, information is transferred by the selective deposition of charged areas on the tape so that the information is represented by the pattern of charge and uncharged areas, as shown in the enlarged tape area and identified by the legend latent image. The tape passes to the left, as viewed in FIG- URE 1, over a roller 36 supported at the extremity of dancer arm assembly 37, the upper portion of which is journaled in a fixed support (not shown) of the equipment. Tape moves over roller 36 and to the right, passing over another roller 38 disposed adjacent and beneath the inking station.

As the tape enters the inker and passes upwardly, it engages the extremity or lip of a flexible seal 39. The tape progresses upwardly past spacer unit 40 and ink level baffle 41, and past the face of an air deflection unit 4-2. The portion of unit 42 proximate the path of tape travel is shaped to deflect air moving upwardly, redirecting the air downward so that minute powder particles entrained in the air stream will be returned to the bottom of the inking assembly. The tape then passes adjacent a heater 43 which in the illustrated embodiment is hexagonal in section. The beater is rotated continually when the system is energized, so that the projections of the beater successively engage and agitate the tape to displace therefrom any particles which may tend to adhere to the noncharged or background areas of the tape. Above the heater is the operating portion 44 of a lift-off arm assembly 45, the opposite end of which is coupled to a rotary solenoid 46. As this assembly is energized, portion 44 is displaced 4t through a short, predetermined operating stroke to engage the tape and displace the tape away from beater 43 to prevent undesired marking of the tape. Another spacer unit .7 is positioned just above the extremity 44 of the lift-off arm assembly.

Near the top of the inker three air deflecting elements 4%, 49 and 5d are shown. Such elements may be separate air deflecting elements of a configuration and purpose analogous to those of unit 42, or they may be separate extensions of a complete assembly to facilitate fabrica tion and installation within the inker. At the top of the inker mechanism a guide pin 51 is positioned so that as the tape leaves the inker, a sharp and sudden turning movement is provided to assist in dislodging any particles which may adhere to the background portions of the tape.

On the tape as it leaves the inker the information is represented visibly but as yet is not permanently affixed. The tape, with the ink or powder particles adhering to the charged areas, passes between upper and lower rollers 52 and 53 at the pressure fixing station 24. A lever assembly 54 is provided and journaled about a suitable pivot 55 to effect displacement of the upper roller 52 away from and back into engagement with the lower roller, thus to facilitate the lateral insertion of the tape into this portion of the system. The lower roller 53 is journaled on a shaft 56, and drive to the shaft is provided by a clutch unit 57 and a motor 58. In addition a brake unit 59 is provided to halt shaft 56 as drive to other portions of the system is terminated. After the tape with the pressure-sensitive coating passes between rollers 52 and 53, the image is permanently affixed thereon as indicated by the enlarged portion of the tape and the legend fixed image.

The tape again changes direction as it moves over roller 60, and then is wound on take-up roller 25. With this general perspective of the system as a whole, the interconnection and cooperation of various portions of the controls for the system will now be described.

System intercoupling and control Considering first the circuitry of the equipment depicted in FIGURE 2, reference characters 66 and 67 designate input conductors over which electrical energy, in the form of alternating-current (A-C) power, is applied to the equipment from commercial power lines (not shown). A fuse 68 is coupled between conductors 66 and 65 to function as an isolation means and prevent high current surges from damaging the equipment and likewise to prevent damage to associated units should a short circuit or other fault occur within the equipment. An on-off switch 69 is provided with a normally-open contact set 70 and a normally-closed contact set 71. It will be apparent that the movable contact is connected to both the normallyopen and to the normally-closed contact sets, with each set also including an individual fixed contact. For purposes of the present explanation, the normally-closed contact set will in general be referred to as the back contacts, or back contact set, and the normally-open contact set will be characterized as the front contacts or front contact set. The fixed contact of front contact set 70 is coupled over conductor 65 and fuse 68 to input conductor 66, and the movable contact of switch 69 is coupled to one end of winding 72 of the power relay 73, which includes contact groups 74 and 75. Contact group 74 includes a back contact set 76 and a front contact set 77, and group includes a back contact set 78 and a front contact set 79. In the operated position of relay 73, input energy is translated from input conductors 66 and 67 over the respective contact sets '79 and 77 to conductors 80 and 81. Terminals 82 and 83 are coupled to conductors 8t) and 81, respectively, to provide A-C energy for energizing associated equipment as soon as power switch 69 is thrown to operate relay 73. Power is also applied from conductors 80 and 81 across the primary winding 84 of the transformer 85, and to both sides of the capstan drive motor 86 (for driving fixed capstan roller 32 in FIGURE 1) and to the pressure fixer motor 58, which is depicted generally in FIGURE 1.

More specifically, it is noted conductor (FIGURE 2) is coupled over circuitry including a phase-shifting or phase-splitting capacitor 87, the other side of which is electrically coupled to motor 86. Conductor 80 is also coupled over a fuse 88 to a starting relay 89 for the pressure fixed motor, which starting relay includes a winding 90 and a contact set 91. A current limiting resistor 92 is series-coupled between one side of motor 58 and the relay unit 89, and the other side of the pressure fixer motor 58 is coupled to conductor 81.

It is also noted that conductors 80 and 81, together with a common ground conductor 93, are utilized for transferring AC input power to a D-C power supply unit 94. Responsive to the application of AC energy, a plurality of D-C voltages of various amplitudes and polarities appear on the respective output conductors indicated along the lower portion of unit 94. In this embodiment, only the conductor pair at the far right comprising negative conductor and common ground conductor 93 will be described. Although a potential of minus fifty volts with respect to ground appeared on conductor 95 in a preferred embodiment, it will be apparent to those skilled in the art that various polarities and amplitudes can be utilized depending upon the exact equipment to be energized and the control function to be performed.

A microswitch 96 is provided with its armature or movable contact coupled to conductor 80. This switch includes a back contact set 97 and front contact set 98, with no electrical connection made to the fixed contact of the back contact set. The contacts of switch 96 are in the position indicated when the rollers 52 and 53 (FIGURE 1) of the pressure fixing station are spaced apart from each other, and front contacts 98 are closed as roller 52 is moved downwardly to press the tape firmly between the pair of rollers. The fixed contact of set 98 is coupled over conductor 100 to another position-sensitive switch 101, which includes back contacts 102 and front contacts 103. Switch 101 is in the illustrated position with contacts 102 closed when the dancer arm 37 is displaced from the position indicated in FIGURE 1 to the right, to the load position of this equipment. The point at which contacts 102 close as the dancer arm is moved to the right is shown in FIGURE 3. As will be made clear hereinafter, the drive equipment for the pressure fixing station is adjusted so that motor 58 tends to drive the tape past this station at a speed approximately ten percent faster than the rate at which capstan unit 30 rnoves the tape. Thus, to avoid tape breakage, clutch 57 must be regulated to continually interrupt and return positive drive to roller 53, and this regulation is obtained from the position of the dancer system the tape is initially displaced only at drive capstan 30. Accordingly, the position of dancer arm 37 must be such that it can move in a clockwise direction, as viewed in FIGURE 1, to take up slack tape during the initial operation of the system and start the driving of roller 53 (by closure of contacts 168) at the proper time. Before this operation commences, when the roller 36 at the bottom of the dancer arm is positioned at the right, in the load position, contacts 102 are closed, and these contacts extend the potential appearing on conductor 100 over conductor 104 to another switch 105, including back contacts 106 and front contacts 107. Switch is a ready switch, and is actuated momentarily to effect the operation of ready relay 108, which includes a winding 109 coupled to front contacts 107 of the ready switch. The ready relay further comprises a first contact group 110, including back contacts 111 and front contacts 112, which function to provide a holding circuit for the relay; a second contact group 113, having a back contact set 114 coupled to an indicator lamp 115 and a front conarm. Upon energization of the Resistor 183,

tact set 116 coupled to another indicator lamp 117 with the common or movable contact of this group being coupled over a resistor 118 to one end of the secondary winding 119 of transformer 85; a third contact group 120, having back contacts 121 and front contacts 122, with this contact group being used in controlling selective driving and braking of the pressure fixer unit and lift-off solenoid in a manner to be explained hereinafter; and a fourth contact group 123, having unconnected back contacts 124 and a front contact set 125 for extending the control potential on conductor 95 toward the control circuits for regulating the tape drive and braking at the capstan drive unit adjacent the printing station. Another indicator lamp 128 is series-coupled with resistor 129, and this combination is coupled in parallel across secondary winding 119 of transformer 85. A resistor 126 and a capacitor 127 are series-coupled, and this combina tion of element is connected in parallel across winding 109, to regulate the operating characteristics of this relay.

The fixed contact of front contact set 125 is coupled to a common conductor 130, which conductor is coupled over an indicator lamp 131 and conductor 132 to the solenoid driver assembly unit turn coupled over conductors 134 and 135 to a start/stop board assembly 136. For purposes of the present explanation, it is sufiicient to note that, responsive to signals applied from the start/stop board over conductors 134 and 135, circuitry within the solenoid driver assembly 133 provides a connection between a plane of reference potential, such as ground, and one of the conductors shown at the left of unit 133, to complete an energization circuit for either brake unit 27 or pinch roller 31. Coupled in parallel with indicator lamp 131 is a series combination of a dropping resistor 137 and an energizing winding 138 for displacing the capstan pinch roller 31 into its operating position. Accordingly, when an operating potential appears across winding 138 the capstan pinch roller is displaced into operating position to start movement of the tape, and it is therefore evident that lamp 131 is utilized as a start indicator for the system.

Also coupled in series between common conductor 130 and assembly 133 is another indicator lamp 139 and a control winding 140 for regulating displacement of movable shoe 29 of the brake unit depicted in FIGURE 1. through circuitry (not illustrated) within solenoid driver assembly 133, is coupled to winding 140, and functions as a dropping resistor to limit the voltage applied to this winding. One end of brake winding 140 is coupled not only to the stop indicator lamp 139 but also over the conductor 142 to assembly 133. Other circuitry, not shown, within solenoid driver assembly 133 is utilized to effect selective and incremental energization of capstan unit 30 and brake unit 27 to provide tape stepping in those applications where continuous on-thefly printing is not desired.

Below contact group 123 a resistor 143 is coupled between conductor 95 and another conductor 144, in its turn is coupled to each of three different contact groups 145, 145, and 147. Conductor 144 is coupled to the center or movable contact of group 145, having back contacts 148 and front contacts 149. Conductor 144 is further coupled to the fixed contact of back contacts 150 of group 146, which group further includes a front contact set 151. In addition conductor 144 is coupled to the movable contact of group 147, generally engaging the fixed contact of back contacts 152 and displaceable to engage the fixed contact of front contact set 153. The contact group is in the position shown when dancer arm 37 (FIGURE 1) is nearer the load position than the slack tape position. As the dancer arm is displaced in the clockwise direction as viewed in FIGURE 3 past the point referenced 148 CLOSE to the point 149 CLOSE, at the latter point contacts 149 close and thus contacts 148 open. This circuit operation extends a signal over conductor 154 to start/stop board 136. Con- 133, which assembly is in tact group 146 is utilized as a momentary switch, operating simultaneously with group 157, to alternately eifect the transmission of start and stop signals over conductor 155 to board 136. Lastly, contact group 147 is momentarily energized in unison with contact group 185 as the ready switch is momentarily depressed, and translates a corresponding signal over conductor 156 to start/sto board 136.

As noted above contact group 146 is operated concomitantly with contact group 157, shown near the lower left hand portion of FIGURE 2. This contact group includes back contacts 158 and front contacts 155, with the movable or common contact coupled over con-ductor 168 to ground. The fixed contact of set 158 is coupled over conductor 161 to the movable contact of group 162, which group includes a back contact set 163 and a front contact set 164. Contact group 162 is in the position illustrated when the dancer arm is displaced to the right of the position indicated by the legend 163 CLOSE in FIGURE 3. Front contact set 164 is closed and set 163 is opened, as the dancer arm is displaced to the left and passes the position identified 164 CLOSE. The fixed contact of set 159 is coupled over conductor 165 to the movable contact of contact group 166 which includes back contacts 167 and a front contact set 168. Conductor 165 is also utilized to extend the potential at the fixed contact of set 159 to the fixed contact of set 1-63. Another conductor 169 extends the potential at the fixed contact of set 164 both to the fixed contact of set 167 and to a common conductor 170. Contact group 166 is in the position i1lustrated when the dancer arm is in the load position or when there is a little slack in this part of the system. As the amount of slack increases and the dancer arm is displaced to the left as viewed in FIGURES 1 and 3, con tact set 168 is closed at the point identified 168 CLOSE to extend the potential appearing on the movable contact of that set to the movable contact of group 120. The fixed contact of set 122 is coupled over a resistor 171 and winding 172 of clutch 57 (FIGURE 1) to conductor 95, to which the operating potential is applied. A resistor 173 is series-coupled with a capacitor 174, and this combination is coupled in parallel across winding 172. Common conductor 176 is coupled over energizing winding 175 of brake 59 (FIGURE 1) and the parallel-connected combination of resistor 176 and capacitor 177 to conductor 95. Elements 176 and 177, together with the series-coupled resistor 178 and the capacitor 179 which are connected across winding 175, provide suitable operating characteristics of the brake. Common conductor 171i is also coupled to one side of operating winding 1811 of rotary solenoid 46 (FIGURE 1), and the parallel-connected combination of resistor 181 and capacitor 182 is coupled between the other side of winding 180 and the side of brake winding 175 remote from conductor 176. Accordingly, the lift-off solenoid 46 in FIGURE 1 is energized simultaneously with each energization of brake 59 to halt the movernent of the tape through the pressure fixing equipment.

Considering now the operation of the control equipment shown in FIGURE 2 in relation to the elements depicted in FIGURE 1, a suitable wall plug (not shown) or other conventional means is utilized to apply an energizing A-C potential over conductors 66 and 67, fuse 68 and conductor 65, to the back contact sets of relay 73. Conductor 66 can be considered the hot line and conductor 67 the common line, which extends to one side of winding 72 of the power relay.

Power switch 69 i displaced and at its front contact set 70 completes an obvious energizing circuit for winding 72 of relay 73, which operates and effects the closure of its respective front contact sets 77 and 79 to extend the A-C energizing potential to conductors 86 and 81. The energizing potential on these conductors is applied to the capstan drive motor 86 and to the pressure fixer motor 58. Motor 86 drives lower capstan roller 32 but at this time pinch roller 31 is spaced from the tape and roller 32, so the tape is not displaced. Further, there is no tape iovement by motor 58 until clutch winding 172 is energized. Power is also passed over conductors and 81 to the DC power supply 94, which in its turn extends an operating potential over conductor to back contact set 124 of contact group 123, over conductor 144 to contact groups 145447, and to one side of each of clutch winding 172, brake winding 175, and lift-off solenoid winding 180. From FIGURE 3 it is apparent that with back contacts 167 closed, the dancer arm is positioned to the right of its midpoint of travel. Under these conditions it is not desired to energize the pressure fixer drive motor by energizing clutch winding 172 but rather to maintain this drive equipment deenergized until more slack tape is provided in the system. Accordingly ground potential is extended over conductor 161), contact set 158, conductor 161, contacts sets 163 and 167, to common conductor 170, thus completing energizing circuits both for brake winding 175 and the lift-off solenoid winding 188'. Thus brake 59 in FIGURE 1 is operated to preclude any tape movement in this portion of the system, and rotary solenoid i6 is operated and displaces arm 44 to engage the flexible tape and move it out of engagement with beater 4-3. This stop condition of the system is indicated by the energization of indicator lamp 128 over transformer 85, the primary winding of which is coupled to conductors 8i? and 81. It is noted that lamp 128 signifies the operation of power relay 73 after switch 68 is actuated.

The potential appearing on conductor 88 is also extended to back contacts 97, and as the pressure fixer rollers 52 and 53 are displaced into engagement with each other, front contacts 98 are closed and this potential is extended over conductor 108 to back contacts 102 of the dancer load switch 101, and also to back contacts 111 of group 110. Thus after the pressure fixing rollers are positioned for operation and contacts 98 are closed, relay 188 is conditioned for operation by the momentary actuation of ready switch 185, provided that back contacts 162 are closed to indicate the dancer arm is nearer the load than the slack tape position. Even before ready relay 108 is operated, however, it is noted that the DC energizing potential appearing on conductor 95 is extended over resistor 143, conductor 144, back contacts 150 and conductor 155 to start/stop board 156.

The ready switch is momentarily actuated to close contacts 187 and complete an obvious energizing circuit for winding 169 of ready relay 108, which operates and at its contacts 112 completes an obvious holding circuit to maintain the flow or energizing current through the relay winding after the momentary switch 105 is released. At its contacts 114 ready relay 188 effects the interruption of the energizing circuit for the load indicator lamp 115 and at its contacts 116 completes an energizing circuit for the ready lamp 117. In its operation relay 188 also closes front contact set 122, but inasmuch as the dancer arm is to the right of its center position at this time, contacts 168 are open and therefore ground potential is not extended to the left side of clutch winding 172. Relay 168 in its operation also effects the closure of contacts and thus extends the operating potential from conductor 95 to common conductor 1511. Accordingly, whether capstan drive winding 138 (for pinch roller 31) or the brake Winding 146 (for displacing shoe 29) will be energized at this time depends upon selective application of ground potential to one or other of the conductors 132 and 141, which in turn depends upon the receipt of control signals over, conductors 134 and 135 from start/ stop board 136.

To commence driving of the tape through the system, the start/stop switch 146 is momentarily depressed, closing each of contact sets 159 and 151. Closure of contact set 159 does not otherwise affect the circuitry, in that the dancer arm is still to the right of its center position and contact set 168 is still open. Accordingly, brake winding 175 and lift-oft solenoid winding 180 are still energized. Closure of contact set 151 of switch 146 is effective to extend ground potential over conductor 155 to start/ stop board 136. The circuitry within board 136 translates over conductors 134 and 135 a signal which, in effect, applies ground potential to conductor 132 adjacent solenoid driver assembly 133. In that operating potential has already been applied over contacts 125 to conductor 130, control winding 138 is energized and pinch roller 31 is displaced downwardly to positively engage the tape with roller 32, driving the tape past the printing head,

and at the same time start lamp 131 is illuminated to signal this operation. It is noted that at this time the tape is not being driven past pressure fixing station 24.

As the tape begins to move past the drive capstan, the amount of slack increases and the dancer arm is displaced to the left under the urging of a bias unit (not shown) such as a spring, past the center position, effecting the opening of contacts 167 and the closure of contacts 168. The opening of contact set 167 interrupts the energizing circuit for fixer brake winding 175 and lift-ofl solenoid winding 180, thereby deenergizing these units. Closure of contacts 168 extends ground potential from conductor 160 over these contacts and contact set 122 to the left side of fixer clutch winding 172, completing the previously prepared energizing circuit for this unit and energizing clutch 57 to drive roller 53 and positively displace the tape through the pressure rollers toward the take-up reel. Because tape speed at this location is about ten percent higher than the tape speed at the capstan, the amount of slack tape diminishes, and the dancer arm moves to the right (FIGURE 1). Such movement opens contacts 168 to deenergize clutch winding 172, and closes contact set 167 to energize both brake winding 175 and lift-off solenoid winding 180. The amount of slack tape again increases, the dancer arm moves to the left, contacts 168 close and 167 open, clutch 57 is again energized as the brake and lift-off solenoid are deenergized, and this cycle is continually repeated during system operation as the dancer arm is displaced back and forth through the interval'designated 166 in FIGURE 3.

To halt movement of tape through the system, the momentary'start/stop switch 146 can be actuated to again effect a momentary closure of contact sets 151 and 159. The ground potential signal is extended over conductor 155 and through suitable flip-flop circuits in the start/ stop board and the solenoid driver assembly to remove ground potential from conductor 132 and to apply ground potential to conductor 141, completing the energizing circuit for control winding 140 of brake unit 27, Removal of ground potential from conductor 132 interrupts the energizing circuit for capstan pinch roller winding 138. Accordingly a retarding force is provided by brake unit 27 even as drive capstan pinch roller 31 is displaced away from thevtape and from roller 32 to effect a positive halting of the flexible tape. However, momentarily there remains a slight movement of the tape between the pressure fixing rollers 52 and 53. Accordingly the amount of slack in the system rapidly diminishes, moving the dancer arm 37 from the slack position as illustrated in FIGURE ltoward the right into the load or no-slack position. As the dancerarm reaches the no-slack position, contact set 168 is opened to interrup energization of clutch winding 172, and contact set 167 is closed, completing the energizing circuit for brake control winding 175 and lift-off solenoid winding 189. Thus the two positive drives, adjacent the printing station and at the pressure fixing station, are removed from the system while the brake unit 27 and the brake 59 at the pressure fixing station 24 are energized to rapidly and positively halt tape movement.

Painting head The printing (or charging) head and certain views 16 present invention will now be described. FIGURE 4 depicts the printing head 33 afiixed to a mounting or support plate 199, which defines a pair of aligning apertures 191 and 192 for properly positioning the complete assembly on a support wall (not shown). An important feature of the invention, an occlusion means or mask assembly 193, is shown at the bottom of the charging or printing head, and common electrode or anvil unit 34 is spaced from the mask assembly at a small interval. This interval, in a preferred embodiment, was of the order of ten or twelve mils (thousandths of an inch). The tape 20 passes through the system as indicated, with the lower or conducting surface of the tape actually engaging electrode 34 and the upper or non-conductive' surface of the tape spaced from the mask assembly. A movable tape guide unit 195 is pivotally mounted to be retained in the position indicated in FIGURE 4 by a spring 196, and as shown in FIGURE 7 tape guide 195 is rotatable about a pivot axis or pin 197 against the urging of bias spring 196 into a load position displaced from the operating position depicted in FIGURE 4. FIGURE 7 also shows a mounting and adjusting screw 198 for retaining the anvil assembly against mounting plate 190, and bias spring 196 is fastened to anvil 34 by another screw 211. Because an elongated aperture (not shown) is provided in plate for screw 198, this screw can be loosened to permit adjustment of the position of anvil 34 with respect to the bottom of the mask assembly, and then tightened after the gap distance has been set.

FIGURE 5 shows the charging head with a wall portion 199 partially broken away to show the positions of a plurality of insulated electrical conductors 200' which extend from the external circuit over pin connectors 187 to another circuit in the interior of the printing head, where the conductors are coupled through a plurality of impedances 291 (here shown as resistors) to a like plurality of individual conductors 202, in turn connected to the respective electrode arrays at the bottom or operating portion of the printing head. In a preferred embodiment the printing head 33 includes an insulating wall portion 136 from which a plurality of male connectors 187 extend, to establish connection with corresponding female connectors (not shown) coupled to the respective conductors 200. Such an arrangement provides for the simple and rapid exchange of individual printing heads, which may be desirable to provide separate printing heads with different values of the resistors 201 to effect variation of the system printing characteristics as will be explained hereinafter.

As shown in more detail in FIGURE 6, each of the conductors 202 passes downwardly and, as these conductors converge in the operating portion of the printing head, they are supported in respective blocks of insulating material 203 and 294, which blocks are effectively separated by a thin insulator 205 of quartz or other suitable material. The materials for these elements together with the techniques for their fabricaiion are disclosed and claimed in the patent identified above. In FIGURE 6, in addition to the plurality of conductors Z02, another conductor 214 is provided to effect electrical intercoupling between the conductive mask-and-spring assembly and the circuitry external to the printing head.

At the bottom or working face of the head, the mask assembly 209 is fixed to a mounting spring 206, and these elements are also shown in FIGURE 9. This entire assembly is supported, as shown in FIGURE 6, by a pair of mounting springs 188 (only one of which is shown). Each spring 188 has a base portion secured by screws 189 to the lower portion of the printing head, and finger portions which extend beneath the mask assembly as shown to retain the mask in place. The mask is readily removed by sliding it laterally away from plate 190, and can be replaced in a similar manner. The mask, as seen in FIGURE 9, includes a plurality of apertures 11 207, and one aperture 208 is of a configuration different from the others. This is in accordance with the practice, when required, of providing a sprocket or guide mark on the tape at regular intervals to provide a reference mark which does not vary with the other information imprinted on the tape.

In the partial side view of FIGURE 7, each of the individual electrode arrays 210 is shown. The term array is used to describe all the electrodes, usually sup ported in charge head 33 which cooperate in imparting one mass of charge particles at one spot on the tape. The term array does not include the grounded or anvil electrode 34, or the mask unit 209, which is not always used. In this side view, only two electrodes of each array are visible but each array includes four conductors symmetrically positioned as will be described hereinafter. Other details of the anvil 34, tape guide 195, and bias spring 1% are also visible in FIGURE 7.

The enlarged view of FIGURE 8 indicates generally the placement of the individual electrode arrays, as seen looking upwardly from the conductive tape toward the mask defining apertures 207. Although the conductors have previously been referenced by numeral 202, for purpose of explanation in FIGURE 8, the input electrodes are designated 212 and the output electrodes are designated 213. The body of the mask 209 obviates the movement of charged particles therethrough and the particles can only pass through opertures 207 to reach the tape. It is important to note that, without any mask between the charging head and the anvil, a markedly superior performance has been obtained by utilizing more than two electrodes in each individual array of electrodes. That is, with the use of four electrodes such as those referenced by numerals 212 and 213 in FIGURE 8, excellent results have been obtained in the production of sharply defined and opaque dots or marks on the printing tape after the powder is permanently affixed at the pressure fixing station. A further improvement can be realized with the addition of a mask or occlusion means, even of non-conductive material, but the improvement obtained by utilizing more than two electrodes in each array even without a mask is substantial.

FIGURE 10 shows, in a simplified manner, the energiza-tion of a single array of electrodes 212 and 213 disposed over a portion of anvil 34. The resistors 201 shown generally in FIGURE have been replaced in FIGURE by variable resistors or potentiometers 215 intercoupled between pulse control unit and input electrodes 212, and by variable resistors 216 intercoupled between output electrodes 213 and a common conductor 217, in its turn connected to a plane of reference potential or ground. It is apparent that, with the circuitry illustrated in FIGURE 10, both (1) the total resistance in the discharge circuit (that is, the sum of the resistance between the pulse control unit 35 and conductor 217) can be varied, and in addition (2) the resistance ratio, the ratio of the total resistance in either the input leg (between unit 35 and electrodes 212) or the output leg (between electrodes 213 and conductor 217) in relation to the total resistance in the discharge circuit, can also be varied. As noted previously, the variation of these parameters with more than two electrodes in a single array serves not only to enhance the quality of the printed marks but also to regulate various characteristics, such as the effective width, density and definition of the charge areas.

FIGURE 11 depicts an embodiment of the invention similar to that shown in FIGURE 10, but further including a mask 2119, of which a portion defining an aperture 207 is shown. It has been found that with the mask comprised of non-conductive material, improved definition of the charged areas has been obtained. Further improvements have also been realized with the mask either constructed of conductive material or comprised of a base member formed of non-conductive material and overlayed with a layer of conductive material, such as can be applied by a conductive paint. In the embodiment of FIGURE 11, when the mask is provided of conductive material, the mask floats with respect to the other portions of the circuit.

FIGURE 12 shows another embodiment of the invention in which a D-C bias stage 218 is intercoupled between the mask and a plane of reference potential, such as ground. Good results have been obtained with a constant potential applied to the mask, and adjusting means can be provided (as represented by an adjusting knob 219) to vary the level'of the bias potential and thereby alter the characteristics of the charged areas. In the limiting case, the D-C bias potential can be reduced to zero, thereby applying ground potential to the mask.

In the showing of FIGURE 13, a voltage divider arrangement has been provided to apply a pulsed or alternating bias to the mask. As there shown, a potentiometer 220 having an adjustable arm 221 is intercoupled between pulse control unit 35 and ground. Movable arm 221 is coupled to mask 209, so that a proportionate part of the discharge pulse (as determined by the setting of arm 221) is applied to the mask when, and only when, the discharge occurs between the input and output electrodes. Very good results have been obtained with this arrangement, and the power requirements have been diminished by reducing the time during which the bias is applied. In some cases a combination of D-C bias and pulsed bias isused, and this arrangement is obtained by the indicated coupling of the D-C bias unit 218 to the top of the pulse divider potentiometer 220.

For purposes of illustration and of explanation, the resistors 215 and 216 have been indicated as variable in that the adjustment of 1) the total amount of resistance be tween pulse control unit 35 and ground is made variable to produce a modification of the printing characteristic, and (2) the ratio of the amount of resistance between the input electrodes and unit 35 divided by the amount of resistance in the discharge circuit is also variable to modify the printing characteristic. In actual practice it has been found desirable to make these resistors fixed, that is, of a single value, so that a given printing head produces code and alphanumeric characters of a given form. However the printing head is made readily removable so that a different printing head, with different values of resistance in the input and output legs, can be inserted to produce a desired printing characteristic. Such an interchange is analogous to the simple removal and replacement of the printing head on those typewriters where the head moves across the paper and the letter forms on the head are all of a given type style.

Summary Utilizing the inventive principles a substantially improved electrostatic printing head has been provided. Important to the realization of the improved operating characteristics is the provision of more than two electrodes in each array which forms an individual charged area, the variation of the total resistance between the pulse unit and ground, and the variation of the resistance ratio which is a quotient of the resistance in either of the input and output legs divided by the total resistance in the discharge circuit. Different printing characteristics can be obtained by simply removing the charging head and inserting a second head having different values of resistance in the input and output legs.

While certain embodiments of the invention have been illustrated and described in setting forth the inventive principles it is manifest that modifications and alterations may be made therein. It is therefore the intention in the appended claims to cover all such modifications and alterations as may fall within the true spirit and scope of the invention.

What is claimed is:

1. In a system for impressing electric charges on a dielectric medium in an information-denoting pattern, a

charging station including an array comprising at least two pin electrodes positioned on the same side of said medium and having extremities disposed in substantially the same plane, which array is operable as energized to produce a discharge between the electrode extremities and provide a single cloud of said electric charges, occlusion means defining an aperture between said array and said medium, the solid portion of said occlusion means blocking certain of said electric charges and said aperture pass ing others of said electric charges to shape said cloud of electric charges and thus regulate the definition of the charged area deposited on said medium, means for applying a bias voltage to said occlusion means to assist in displacing said cloud of electric charges through said aperture to provide a charged area on said dielectric medium, and means for effecting relative movement between said array and said medium as said array is selectively energized to provide on the medium an information pattern comprising charged and non-charged areas.

2. In a system for selectively applying electric charges on a dielectric medium to denote specific information, a charging station including a printing head comprising a plurality of electrode arrays, each array including more than two electrodes, said arrays being disposed on one side of said medium for energization to produce charged areas on the adjacent portions of the medium, an electrically conductive mask assembly interposed between said arrays and said medium, said mask assembly defining a plurality of apertures, each aperture being in registration with one array to regulate the definition of the charged areas, means for effecting relative movement between the printing head and the medium as the arrays are selectively energized, and bias means coupled to said mask assembly for applying a pulsating bias potential to said mask assembly, the pulses being applied in timed relation with the energization of said electrode arrays, for modifying the definition of the charges deposited on the medium.

3. In a system for selectively applying electric charges on a dielectric medium to denote specific information, a charging station including a printing head comprising a plurality of electrode arrays, each array including more than two electrodes, said arrays being disposed on one side of said medium, pulse producing means for ener gizing said arrays to produce charged areas on the adjacent portions of the mediums, a mask assembly interposed between said arrays and said medium, said mask assembly defining a plurality of apertures, each aperture being in registration with one array to regulate the definition of the charged areas, means for effecting relative movement between the printing head and the medium as the arrays are selectively energized, and voltage divider means having a fixed connection coupled to said pulse producing means and a movable connection coupled to said mask assembly, for applying to said mask assembly a bias potential alternating in time coincidence with the energization of said arrays to thereby modify the definition of the charges deposited on the medium.

4. In a system for selectively applying charged particles to a dielectric medium to denote specific information, a charging station including a printing head comprising a plurality of electrode arrays, said arrays being disposed on one side of said medium for energization to produce charged areas on the adjacent portions of the medium, each of said arrays comprising more than two pin electrodes having extremities disposed in substantially the same plane, means for selectively applying energizing pulses between the electrodes in each array to produce a discharge between the electrode extremities and provide a mass of charged particles adjacent the electrode extremities as the array is energized, an electrically conductive mask assembly interposed between said arrays and said medium, said mask assembly defining a plurality of apertures, each aperture being in registration with one array to regulate the passage of the mass of charged particles from said one array toward the dielectric medium and correspondingly regulate the definition of the charged areas, means for effecting relative movement between the printing head and the medium as the arrays are selectively energized, an anvil electrode positioned on the side of said medium remote from the mask assembly, and means for applying bias potentials to said printing head, said mask, and said anvil electrode, to urge the charged par ticles produced adjacent the printing head through a mask aperture toward the dielectric medium.

5. In a system for selectively depositing charged particles on a dielectric medium to denote information, a charging station including a printing head comprising a plurality of electrode arrays, each array comprising more than two pin electrodes having extremities disposed in substantially the same plane, said arrays being disposed on one side of said medium for energization to produce a discharge between the electrode extremities and provide a cloud of charged particles adjacent each array as energized, an electrically conductive mask interposed between said arrays and said medium, said mask defining a plurality of apertures, each aperture being in registration with one array to regulate the passage of said cloud of charged particles through the aperture toward the dielectric medium and correspondingly regulate the definition of the charged areas, means for elfecting relative movement between the printing head and the medium as the arrays are selectively energized, an anvil electrode disposed on the side of the dielectric medium remote from the conductive mask, and means for applying pulses of bias voltage to said printing head and said conductive mask, said bias pulses being applied in timed relation with the energization of said electrode arrays, for urging the charged particles produced adjacent the electrode arrays through the mask apertures toward the dielectric medium.

6. A system for energization with electrical pulses for electrostatically recording on a recording medium coupled to a reference potential, wherein said pulses have a substantially high magnitude with respect to said reference potential, including a recording head comprising a plurality of pairs of pin electrodes for producing electrical discharges therebetween, one electrode of each pair having one extremity positioned adjacent one extremity of the other electrode of such pair, a high dielectric medium for electrically separating the electrodes of each pair such that the discharge occurs at the extremities of such pair, means for selectively applying said pulses between'the electrodes of each pair to produce an electrical discharge between the extremity of said one electrode and the extremity of the other electrode of such pair, a resistance means coupled between said other electrode of such pair and said reference potential so that, as current flows through said resistance means resultin from said discharge, a potential of a level sufficient to accelerate ions produced as a result of said discharge to said recording medium is developed across said resistance means, and conductive electrode means interposed between selected ones of said pairs of electrodes and said recording medium, said conductive electrode means defining an aperture therein which is shaped to control the configuration of the flow of ions being accelerated towards said recording medium.

7. A system as set forth in claim 6 and further comprising means, coupled to said conductive electrode means, for applying a DC bias potential to said conductive electrode means.

8. A system as set forth in claim 6 and further comprising means, coupled to said conductive electrode means,

for applying a pulsating bias potential to said conductive electrode means, the pulsating bias potential being applied in timed relation with the application of said pulses to said pin electrodes.

9. A system for energization with electrical pulses for electrostatically recording on a recording medium, including a recording head comprising at least a pair of 15 in spaced apart relationship Within a gaseous medium, the pin electrodes having extremities positioned in substantially the same plane, an apertured mask supported between said plane and said pulses to at least one of said pin electrodes to cause an dielectric medium, means for applying said electrical discharge in said gaseous medium between the extremities of said electrodes to produce a cloud of ions, and means, including said pin electrodes and said mask, for moving said cloud of ions through the mask aperture toward said dielectric medium, so that the ion cloud is conformed to the mask aperture configuration before striking the dielectric medium.

pin electrodes supported References Cited UNITED STATES PATENTS 3,004,819 10/ 1961 Anderson 346-74 16 Innes et al. 346-74 Benn et al. 346-74 Childress et al 346-74 Metzger 346-74 Joyce 34674 Johnson 34674 Benn et al. 34674 Mayo et al 250-495 Rosenthal 250-495 Haacke 250-495 Walkup 250-495 BERNARD KONICK, Primary Examiner.

I. L. SRAGOW, Examiner. 15 F. C. WEISS, V. P. CANNEY, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,372 ,400 March 5 1968 Herman Epstein et al.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 15, lines 5 and 6, "pulses to at least one of said pin electrodes to cause an dielectric medium, means for applying said electrical" should read dielectric medium, means for applying said electrical pulses to at least one of said pin electrodes to cause an electrical Signed and sealed this 24th day of March 1970.

(SEAL) Attest:

Edward M. Fletchet,]r. E.

Attesting Officer Commissioner of Patents 

1. IN A SYSTEM FOR IMPRESSING ELECTRIC CHARGES ON A DIELECTRIC MEDIUM IN AN INFORMATION-DENOTING PATTERN, A CHARGING STATION INCLUDING AN ARRAY COMPRISING AT LEAST TWO PIN POSITIONED ON THE SAME SIDE OF SAID MEDIUM AND HAVING EXTREMITIES DISPOSED IN SUBSTANTIALLY THE SAME PLANE, WHICH ARRAY IS OPERABLE AS ENERGIZED TO PRODUCE A DISCHARGE BETWEEN THE ELECTRODE EXTREMITIES AND PROVIDE A SINGLE CLOUD OF SAID ELECTRIC CHARGES, OCCLUSION MEANS DEFINING AN APERTURE BETWEEN SAID ARRAY AND SAID MEDIUM, THE SOLID PORTION OF SAID OCCULSION MEANS BLOCKING CERTAIN OF SAID ELECTRIC CHARGES AND SAID APERTURE PASSING OTHERS OF SAID ELECTRIC CHARGES TO SHAPE SAID CLOUD OF ELECTRIC CHARGES AND THUS REGULATE THE DEFINITION OF THE CHARGED AREA DEPOSITED ON SAID MEDIUM, MEANS FOR APPLYING A BIAS VOLTAGE TO SAID OCCLUSION MEANS TO ASSIST IN DISPLACING SAID CLOUD OF ELECTRIC CHARGES THROUGH SAID APERTURE TO PROVIDE A CHARGED AREA ON SAID DIELECTRIC MEDIUM, AND MEANS FOR EFFECTING RELATIVE MOVEMENT BETWEEN SAID ARRAY AND SAID MEDIUM AS SAID ARRAY IS SELECTIVELY ENERGIZED TO PROVIDE ON THE MEDIUM AN INFORMATION PATTERN COMPRISING CHARGED AND NON-CHARGED AREAS. 